Only if they never saw the original casting
While you may be able to hide the glowing bead, you won't be able to hide the yellow light flashing to it's destination.
Delayed Blast Fireball states (PHB 230-1):
A beam of yellow light flashes from your pointing finger, then condenses to linger at a chosen point within range as a glowing bead for the duration.
Minor Illusion can be (PHB 260):
no larger than a 5' cube
The bead is likely contained within that 5' minor illusion, but the path it takes to get there can still be seen. This applies whether you took the action to create the Minor Illusion before or after you cast the Delayed Blast Fireball.
If no one was there to witness the casting, then it would be possible to conceal the bead within a Minor Illusion.